Semiconductor device having structure capable of suppressing oxygen diffusion and method of manufacturing the same

ABSTRACT

A semiconductor device is provided. The device includes a substrate; a gate dielectric film formed on the substrate; a gate electrode formed on the gate dielectric film, and source and drain electrodes, wherein a boundary between the gate dielectric film and the substrate is formed with an F (fluorine)-terminated surface to serve as a barrier for preventing oxygen diffusion.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Korean Patent ApplicationNumber 10-2014-0015458 filed on Feb. 11, 2014, the entire contents ofwhich are incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device, and moreparticularly to, a semiconductor device having a structure capable ofsuppressing oxygen diffusion and a method of manufacturing the same.

2. Description of Related Art

A semiconductor device technology, including a MOSFET (metal oxidesemiconductor field effect transistor) having excellent on/offcharacteristics of an electronic device, has been rapidly developedthrough miniaturization and integration on the basis of silicon since1960's, becomes a core technology of current mobile computing andcommunication devices and is widely applied to a variety of fields.

A method of manufacturing a device including the MOSFET is describedwith reference to FIG. 1. The method comprises processes of forming aMOSFET device part having a gate consisting of a gate dielectric film 2and a gate electrode 3, a source and a drain on a semiconductorsubstrate 1, depositing an interlayer insulation film 4, forming contactholes 5 penetrating therethrough, filling the contact holes 5 with aconductive material 6 and forming a metal wiring 7. The device includingthe MOSFET has merits that the on/off characteristics are more sensitivethan the other devices and miniaturization and integration thereof canbe made by making the gate electrode small, making the gate dielectricfilm thin and increasing a dielectric constant while minimizing a changein process facilities.

In order to enable the MOSFET to smoothly operate, it is important toadjust electrical properties by adjusting characteristics of therespective thin film materials. For example, a research for changingmaterials of the MOS structure of which a substrate, a channel, adielectric film and a gate electrode material are Si, SiO₂ and/orpoly-Si into a high-mobility channel such as Ge or group compoundsemiconductor, a dielectric film having a high dielectric constant(high-k) such as HfO₂ and a metal gate electrode having no depletion ofcharges has been actively carried out. For the metal wiring, in order tofurther reduce the dielectric constant of the interlayer dielectric film4 and to thus reduce an RC delay, a method of introducing a materialsuch as SiOC to manufacture a device has been studied and developed.

In the meantime, the semiconductor device manufacturing method includesseveral tens to hundreds of processes. In order to increase a yield ofthe device manufacturing process, it is important to maintain and securethe characteristics of the materials, which are used for the MOSFETdevice manufacturing process, even when the materials are subject to athermal process, in which the diffusion speed between the materialsincreases, and an oxygen introduction process, particularly, forexample. In particular, the diffusion speed of the oxygen is fast andmost of oxidation reactions are thermodynamically stable, so that theoxygen causes an unwanted oxidation process of the material used for thesemiconductor process, which again causes physical and chemicalreactions such as a volume expansion and a change in composition. A wetcleaning process of the related art, which is performed so as to clean asurface before the deposition or after the etching, is focused to removethe surface contaminants. That is, there is no effect such as diffusionsuppression through surface modification. When impurities increase inthe gate dielectric film or a composition thereof is changed evenslightly, an electrical trap is formed to deteriorate the electricalcharacteristics of the gate dielectric film. In a case of the high-kdielectric film, when the oxygen diffusion occurs, a non-uniform oxidefilm grows between a channel layer of the substrate 1 and the gatedielectric film 2, so that the dielectric constant may be decreased.Also, when the oxygen diffusion occurs in a direction facing towards thegate electrode 3 from the gate dielectric film 2, a leakage current ofthe gate dielectric film may be increased. Also, the oxygen diffusioninto the interlayer insulation film 4 may cause an increase in thedielectric constant, thereby reducing the device operating speed.

The information disclosed in the Background of the Invention section isprovided only for enhancement of (or better) understanding of thebackground of the invention, and should not be taken as anacknowledgment or any form of suggestion that this information forms aprior art that would already be known to a person skilled in the art.

BRIEF SUMMARY OF THE INVENTION

Various aspects of the present invention provide a semiconductor deviceand a method of manufacturing the same capable of suppressing an oxygendiffusion to prevent a semiconductor device from being deteriorated dueto the oxygen diffusion occurring during the manufacturing process andto increase a yield of the semiconductor device manufacturing process.

In an aspect of the present invention, provided is a semiconductordevice including a substrate; a gate dielectric film formed on thesubstrate; a gate electrode formed on the gate dielectric film, andsource and drain electrodes, wherein a boundary between the gatedielectric film and the substrate is formed with an F(fluorine)-terminated surface to serve as a bather for preventing oxygendiffusion.

According to an illustrative embodiment of the present invention, aboundary between the gate dielectric film and the gate electrode mayalso be formed with the F-terminated surface.

According to an illustrative embodiment of the present invention, thesemiconductor device may further include an interlayer insulation filmconfigured to cover the gate electrode and the source and drainelectrodes and formed with contact holes configured to lead the gateelectrode and the source and drain electrodes, the contact holes beingfilled with a conductive material to thus form contacts, whereinboundaries between the source and drain electrodes and the contacts andboundaries between the source and drain electrodes and the interlayerinsulation film are also formed with the F-terminated surface.

According to an illustrative embodiment of the present invention, atleast one of a boundary between the interlayer insulation film and thesubstrate, boundaries between the contacts and the interlayer insulationfilm, a boundary between the interlayer insulation film and the gatedielectric film, and a boundary between the interlayer insulation filmand the gate electrode may also be formed with the F-terminated surface.

According to an illustrative embodiment of the present invention, theF-terminated surface may be formed by a dry cleaning process of applyinga plasma gas to a reaction gas comprising nitrogen, hydrogen andfluorine to generate a by-product and volatilizing the by-product.

According to an illustrative embodiment of the present invention, He,Ne, Ar or N₂ plasma gas may be used as the plasma gas.

According to an illustrative embodiment of the present invention,NF₃+NH₃, NH₃+HF or N₂+H₂+HF gas may be used as the reaction gas.

According to an illustrative embodiment of the present invention, asilicon compound insulation material selected from a group comprisingSiO_(x) and SiN_(x), a metal oxide selected from a group comprisingAl₂O₃, HfO₂, ZrO₂, TiO_(x), TaO_(x), LaO_(x), YO_(x) and GdO_(x), ametal nitride or a combination thereof may be used as the gatedielectric film.

According to an illustrative embodiment of the present invention, ametal material selected from a group comprising Al, W, Cu, Pt, TiN, TaN,Ti, Ta and Pt or a silicon metal compound selected from a groupcomprising doped Si, WSi_(x), NiSi_(x), CoSi_(x) and TiSi_(x) may beused as the gate electrode.

According to an illustrative embodiment of the present invention, acompound selected from a group comprising SiO_(x), SiN_(x), SiCO_(X),SiCO_(x)N_(y), SiCO_(x)H_(y) and a combination thereof may be used asthe interlayer insulation film.

In an aspect of the present invention, there is provided a method ofmanufacturing a semiconductor device including the steps of performing adry cleaning process on a surface of a substrate by using a plasma gas,thereby forming an F-terminated surface on the substrate, theF-terminated surface serving as a barrier for preventing oxygendiffusion; forming a gate dielectric film on the F-terminated surface ofthe substrate; forming a gate electrode on the gate dielectric film, andforming source and drain electrodes.

According to an illustrative embodiment of the present invention, themethod may further include a step of performing the same dry cleaningprocess as the dry cleaning process, which has been performed on thesurface of the substrate, on the gate dielectric film to form anF-terminated surface thereon to serve as a barrier for preventing oxygendiffusion before forming the gate electrode.

According to an illustrative embodiment of the present invention, themethod may further include steps of performing the same dry cleaningprocess as the dry cleaning process, which has been performed on thesurface of the substrate, for a semiconductor structure having thesource and drain electrodes to thus form an F-terminated surface thereonto serve as a bather for preventing oxygen diffusion, and forming aninterlayer insulation film, wherein surfaces contacting the interlayerinsulation film are F-terminated.

According to an illustrative embodiment of the present invention, themethod may further include steps of forming contact holes in theinterlayer insulation film, performing the same dry cleaning process asthe dry cleaning process, which has been performed on the surface of thesubstrate, in the contact holes to form F-terminated surfaces, anddepositing a conductive material in the contact holes to form contacts.

According to an illustrative embodiment of the present invention, theF-terminated surface may be formed by the dry cleaning process ofapplying a plasma gas to a reaction gas comprising nitrogen, hydrogenand fluorine to generate a by-product and volatilizing the by-product.

According to an illustrative embodiment of the present invention, theby-product may be (NH₄)_(x)MF_(x) or MF_(x) by-product (M=Si, Ge ormetal).

According to an illustrative embodiment of the present invention, He,Ne, Ar or N₂ plasma gas may be used as the plasma gas.

According to an illustrative embodiment of the present invention,NF₃+NH₃, NH₃+HF or N₂+H₂+HF gas may be used as the reaction gas.

According to an illustrative embodiment of the present invention, theby-product may be formed to have a thickness of 1,000 Å or smaller.

According to an illustrative embodiment of the present invention, theby-product may be volatilized by a heat treatment of 200° C. or lower.

As set forth above, during the semiconductor device manufacturingprocesses, the plasma dry cleaning process using NH₃ and NF₃ gases, forexample, is performed to change the material surface including Si intothe F-terminated surface, thereby improving the chemical stability.Therefore, it is possible to prevent the yield from being lowered due tothe abnormal reaction resulting from the oxygen diffusion during theprocess and to preserve the characteristics of the respective materials.Thus, it is possible to reduce the noise during the device operation,thereby improving the electrical stability of the device. Also, it ispossible to add the dry cleaning process, depending on the materials tobe protected and the processes, so that it is possible to improve orregulate the device characteristics, in correspondence to a variety ofdevice manufacturing processes.

The devices and methods of the present invention have other features andadvantages which will be apparent from, or are set forth in greaterdetail in the accompanying drawings, which are incorporated herein, andin the following Detailed Description of the Invention, which togetherserve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a MOSFET structure of the related art.

FIG. 2 is a pictorial view illustrating a state where a plasma drycleaning process is performed on a substrate surface to make anF(fluorine)-terminated surface thereon in accordance with anillustrative embodiment of the present invention.

FIG. 3 is an XPS analysis result of the substrate surface for which theplasma dry cleaning process has been performed, illustrating that thefluorine exists on the substrate surface with being bonded to Si (i.e.,Si—F bonding).

FIG. 4 is an XPS analysis result after an oxidation treatment of theSiO₂ film using oxygen plasma has been performed after the dry cleaningprocess, illustrating that the F-terminated oxide film is maintained,i.e., that a thickness of an SiO₂ film is not substantially changed evenunder strong oxidation conditions.

FIG. 5 is a pictorial view illustrating a surface state after the drycleaning process has been performed for a gate dielectric film.

FIG. 6 illustrates a MOSFET structure wherein gate electrode filmdeposition and patterning processes are performed to implement a gate ofthe MOSFET structure, impurities are implanted in source and drainregions by a self-aligning way and the impurities of the source anddrain electrodes are activated through a thermal process.

FIG. 7 illustrates a MOSFET structure obtained by depositing aninterlayer insulation film, patterning contact holes, performing the drycleaning processing in the contact holes, filling the contact holes witha conductive material, performing a contact separation process such asetch back, and depositing and patterning a metal film to complete metalwirings to gate, source and drain electrodes, the MOSFET structure beingcapable of suppressing characteristic deterioration due to oxygendiffusion.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to exemplary embodiments of thepresent invention in conjunction with the accompanying drawings. Herein,detailed descriptions of some technical constructions or terms wellknown in the art of the semiconductor device (for example, a MOSFET)will be omitted. Even if such descriptions are omitted, the features ofthe present invention will be apparent to a person skilled in the artfrom the following description.

First, FIG. 2 illustrates a surface state after a Si substrate 1 issurface-treated using a dry cleaning method in accordance with anillustrative embodiment of the present invention. That is, the Sisubstrate 1 is dry-cleaned using plasma. In an illustrative embodiment,the Si substrate 1 was treated with NF₃ and NH₃ gases under conditionsof 70 W, 1 Torr, NF₃ 50 sccm, NH₃ 100 sccm, He 900 sccm for 30 secondsand then annealed with N₂ at 180° C. (a dry cleaning process usingplasma). After the process, an XPS (X-ray photoelectron spectroscopy)analysis was performed for the Si substrate (refer to FIG. 3). As can beseen from F1s peaks, the fluorine exists on the Si surface with beingchemically bonded to Si (i.e., Si—F bonding) (hereinafter, this isreferred to as F-terminated surface). This surface state cannot beobtained by a wet cleaning process using an HF solution and the like.That is, when the dry cleaning process is performed using NF₃ and NH₃gases, (NH₄)₂SiF₆ or SiF_(x) by-product is formed on the substratesurface. When the substrate is subject to an annealing treatment at atemperature below 200° C. (180° C., in the above illustrativeembodiment), the by-product is volatilized. The fluorine (F) originatingfrom the by-product being volatilized forms the Si—F bonding on thesurface of the Si substrate.

The inventors checked whether the Si—F bonding formed as described aboveis stably maintained. That is, after the dry cleaning process, the SiO₂(Si substrate surface) was subject to oxidation conditions using theplasma energy (250° C., 6000 W, O₂ 10 slm (standard liter per minute; 1slm=1,000 sccm) and then the XPS analysis was performed for the surface.As can be seen from F1s peaks of FIG. 4, the F-terminated surface of theSi substrate was maintained even under O₂ plasma oxidation conditions ofstrong oxidizing power. Also, the F-terminated surface of the Sisubstrate could be seen even under O₂ plasma oxidation conditions afterthe dry cleaning process and H₂ anneal (which is a reduction condition).A change in thickness of SiO₂ due to the O₂ plasma oxidation after thedry cleaning process was measured within a measurement error range. Thatis, it means that the F-terminated oxide film (SiO₂) of which thesurface is not changed as regards the O₂ penetration and diffusion ismaintained. Usually, upon the oxidation by the O₂ plasma, the strongeroxidation occurs, as compared to the typical oxidation conditions.However, it is experimentally confirmed that the F-terminated surfacewas maintained without a substantial change in the surface compositionand the thickness even under the strong oxidation conditions (refer toFIG. 4). This means that the oxygen diffusion is suppressed by theF-terminated surface.

In the meantime, the (NH₄)₂SiF₆ or SiF_(x) by-product, which istemporarily formed on the surface of the substrate by the dry cleaningprocess, is preferably formed to have a thickness of 1,000 Å or smallerand is preferably volatilized at a temperature of 200° C. or lower. Thatis, if the by-product is formed to be thicker than 1,000 Å or if theannealing treatment is performed at a temperature higher than 200° C., acontamination due to vapor phase reaction and re-adsorption upon theremoval of the by-product may be caused, and the fluorine (F) diffusionmay increase at the interface, so that it could be difficult to form theF-terminated surface.

Subsequently, a gate dielectric film 2 is deposited and then the samedry cleaning process as the above dry cleaning process is performed toform the F-terminated surface on a surface of the gate dielectric film(refer to FIG. 5). Then, a gate electrode film 3 is deposited, and thegate dielectric film and the gate electrode film are etched to form agate region. In the meantime, as the gate dielectric film 2, asilicon-based dielectric material selected from a group comprisingSiO_(x) and SiN_(x), a metal oxide selected from a group comprisingAl₂O₃, HfO₂, ZrO₂, TiO_(X), TaO_(x), LaO_(x), YO_(x) and GdO_(x), ametal nitride or a combination thereof may be used. However, the presentinvention is not particularly limited thereto. Also, as the gateelectrode film 3, a metal material selected from a group comprising Al,W, Cu, Pt, TiN, TaN, Ti, Ta and Pt or a silicon metal compound selectedfrom a group comprising doped Si, WSi_(x), NiSi_(x), CoSi_(x) andTiSi_(x) may be used. However, the present invention is not particularlylimited thereto. The gate electrode film may be formed using asputtering or a typical deposition method (PVD, CVD and the like).Subsequently, impurities are implanted using the gate as a protectionfilm, a thermal process is performed and the impurities of the sourceand drain electrodes are thus activated, so that a MOSFET structure isformed (refer to FIG. 6).

The same dry cleaning process as the above dry cleaning process isperformed for the MOSFET structure having the source and drainelectrodes and then an interlayer insulation film 4 is formed. As theinterlayer insulation film, a compound selected from a group comprisingSiO_(x), SiN_(x), SiCO_(x), SiCO_(x)N_(y), SiCO_(x)H_(y) and acombination thereof may be used. However, the present invention is notparticularly limited thereto. Subsequently, the interlayer insulationfilm 4 is formed with contact holes by using a photolithography process.The same dry cleaning process as the above dry cleaning process isperformed for the formed contact holes (thereby, a deformation of thecontact due to the oxygen diffusion, which may occur between the contactand the interlayer insulation film, is prevented. That is, the oxygendiffusion is prevented through the dry cleaning process disclosed in thepresent invention, instead of depositing a separate barrier material.),and a conductive material is deposited and etched back to form contacts.Then, a metal film is deposited for the contacts and is patterned toform a meal wiring 7 (refer to FIG. 7). In the meantime, as theconductive material, a metal material selected from a group comprisingAl, W, Cu, Pt, TiN, TaN, Ti, Ta and Pt or a silicon metal compoundselected from a group comprising doped Si, WSi_(x), NiSi_(x), CoSi_(x)and TiSi_(x) may be used.

As can be easily understood from FIG. 7, the dry cleaning process usingthe plasma is performed more than once during the MOSFET devicemanufacturing process. Thereby, an abutting part (boundary) between thegate dielectric film 2 and the substrate 1, boundaries between thesource and drain electrodes and the interlayer insulation film 4, aboundary between the interlayer insulation film 4 and the substrate 1, aboundary between the interlayer insulation film and the contact, aboundary between the gate dielectric film 2 and the gate electrode 3 andthe like are formed with the F-terminated surface, respectively. TheF-terminated surfaces serve as a barrier for preventing the oxygendiffusion. In particular, as described with reference to FIGS. 2 and 3,the F-terminated surface formed by the dry cleaning process ismaintained as it is even under the strong oxidation conditions using theplasma. Therefore, the F-terminated surface is maintained as it is evenduring the typical thermal process and oxygen introduction process ofthe semiconductor device manufacturing process, so that the oxygendiffusion can be prevented. Therefore, it is possible to prevent anon-uniform oxide film from growing between a substrate channel layerand a dielectric film, to prevent an increase in a leakage current dueto the oxygen diffusion through the dielectric film or gate electrode,and the like.

Although the present invention has been described in relation to thecertain exemplary embodiment, it should be understood that the presentinvention is not limited thereto. The foregoing embodiment can be madeinto various alterations and modifications without departing from thescope of the appended Claims, and all such alterations and modificationsfall within the scope of the present invention.

For example, in the above illustrative embodiment, the dry cleaningprocess was performed during the specific process. However, the drycleaning process of the present invention can also be applied to anyprocess in which the oxygen diffusion may be problematic. For example,as shown in FIG. 7, the dry cleaning process of the present inventionmay be performed before the deposition of the interlayer insulationfilm, so that surfaces contacting the interlayer insulation film may beF-terminated.

In the above illustrative embodiment, He was used in the dry cleaningprocess using the plasma. However, the present invention is not limitedthereto. For example, Ne, Ar or N₂ may also be used, in addition to He.

In the above illustrative embodiment, the Si substrate was used, and thedry cleaning process was performed for the Si substrate to form theF-terminated surface, i.e., Si—F bonding. However, the present inventionis not limited thereto. For example, a Ge substrate or a metal oxidesubstrate such as HfO_(x), ZrO_(x) and the like may also be used. Whenthe dry cleaning process is performed for the corresponding substrate,the F-terminated surface is formed on the surface thereof (for example,although not shown and described, it was confirmed that (NH₄)_(x)MF_(x)or MF_(x) by-product (M=Si, Ge or metal) was formed by the dry cleaningprocess of the present invention.

In the above illustrative embodiment, NF₃ and NH₃ gases were used as thereaction gas in the dry cleaning process. However, the present inventionis not limited thereto. That is, any gas including nitrogen, hydrogenand fluorine such as NH₃+HF and N₂+H₂+HF may be used as the reactiongas, inasmuch as it can form (NH₄)_(x)MF_(x) or MF_(x) by-product (M=Si,Ge or metal) as the by-product.

Therefore, the present invention shall be defined by only the claims andtheir equivalents.

1. A semiconductor device comprising: a substrate; a gate dielectricfilm formed on the substrate; a gate electrode formed on the gatedielectric film, and source and drain electrodes, wherein a boundarybetween the gate dielectric film and the substrate is formed with an F(fluorine)-terminated surface to serve as a bather for preventing oxygendiffusion.
 2. The semiconductor device according to claim 1, wherein aboundary between the gate dielectric film and the gate electrode is alsoformed with the F-terminated surface.
 3. The semiconductor deviceaccording to claim 2, further comprising an interlayer insulation filmconfigured to cover the gate electrode and the source and drainelectrodes and formed with contact holes configured to lead the gateelectrode and the source and drain electrodes, the contact holes beingfilled with a conductive material to thus form contacts, whereinboundaries between the source and drain electrodes and the contacts andboundaries between the source and drain electrodes and the interlayerinsulation film are also formed with the F-terminated surface.
 4. Thesemiconductor device according to claim 3, wherein at least one of aboundary between the interlayer insulation film and the substrate,boundaries between the contacts and the interlayer insulation film, aboundary between the interlayer insulation film and the gate dielectricfilm, and a boundary between the interlayer insulation film and the gateelectrode is also formed with the F-terminated surface.
 5. Thesemiconductor device according to claim 1, wherein the F-terminatedsurface is formed by a dry cleaning process of applying a plasma gas toa reaction gas comprising nitrogen, hydrogen and fluorine to generate aby-product and volatilizing the by-product.
 6. The semiconductor deviceaccording to claim 5, wherein He, Ne, Ar or N₂ plasma gas is used as theplasma gas.
 7. The semiconductor device according to claim 5, whereinNF₃+NH₃, NH₃+HF or N₂+H₂+HF gas is used as the reaction gas.
 8. Thesemiconductor device according to claim 1, wherein a silicon-baseddielectric material selected from a group comprising SiO_(x) andSiN_(x), a metal oxide selected from a group comprising Al₂O₃, HfO₂,ZrO₂, TiO_(x), TaO_(x), LaO_(x), YO_(x) and GdO_(x), a metal nitride ora combination thereof is used as the gate dielectric film.
 9. Thesemiconductor device according to claim 1, wherein a metal materialselected from a group comprising Al, W, Cu, Pt, TiN, TaN, Ti, Ta and Ptor a silicon metal oxide selected from a group comprising doped Si,WSi_(x), NiSi_(x), CoSi_(x) and TiSi_(x) is used as the gate electrode.10. The semiconductor device according to claim 3, wherein a compoundselected from a group comprising SiO_(x), SiN_(x), SiCO_(x),SiCO_(x)N_(y), SiCO_(x)H_(y) and a combination thereof is used as theinterlayer insulation film.
 11. A method of manufacturing asemiconductor device comprising the steps of: performing a dry cleaningprocess on a surface of a substrate by using a plasma gas, therebyforming an F-terminated surface on the substrate, the F-terminatedsurface serving as a bather for preventing oxygen diffusion; forming agate dielectric film on the F-terminated surface of the substrate;forming a gate electrode on the gate dielectric film, and forming sourceand drain electrodes.
 12. The method according to claim 11, furthercomprising a step of performing the same dry cleaning process as the drycleaning process, which has been performed on the surface of thesubstrate, on the gate dielectric film to form an F-terminated surfacethereon to serve as a barrier for preventing oxygen diffusion beforeforming the gate electrode.
 13. The method according to claim 12,further comprising steps of: performing the same dry cleaning process asthe dry cleaning process, which has been performed on the surface of thesubstrate, for a semiconductor structure having the source and drainelectrodes to thus form an F-terminated surface thereon to serve as abarrier for preventing oxygen diffusion, and forming an interlayerinsulation film, wherein surfaces contacting the interlayer insulationfilm are F-terminated.
 14. The method according to claim 13, furthercomprising steps of: forming contact holes in the interlayer insulationfilm, performing the same dry cleaning process as the dry cleaningprocess, which has been performed on the surface of the substrate, inthe contact holes to form F-terminated surfaces, and depositing aconductive material in the contact holes to form contacts.
 15. Themethod according to claim 11, wherein the F-terminated surface is formedby the dry cleaning process of applying a plasma gas to a reaction gascomprising nitrogen, hydrogen and fluorine to generate a by-product andvolatilizing the by-product.
 16. The method according to claim 15,wherein the by-product is (NH₄)_(x)MF_(x) or MF_(x) by-product (M=Si, Geor metal).
 17. The method according to claim 15, wherein He, Ne, Ar orN₂ plasma gas is used as the plasma gas.
 18. The method according toclaim 15, wherein NF₃+NH₃, NH₃+HF or N₂+H₂+HF gas is used as thereaction gas.
 19. The method according to claim 15, wherein theby-product is formed to have a thickness of 1,000 Å or smaller.
 20. Themethod according to claim 15, wherein the by-product is volatilized by aheat treatment of 200° C. or lower.